Report on Health Consequences of Wood Smoke
Recent studies on the emissions of wood burning reveal that in most
northern U.S. cities, wood smoke is a significant contributor to overall
community air pollution. The same is true in the urban areas of the
Wasatch Front. If wood smoke were evenly distributed throughout the
airshed, it would be roughly quantitatively equivalent to all vehicle
emissions in the same region. But wood smoke is not evenly distributed. It
concentrates heavily near its sources, subjecting neighbors to
extraordinarily high levels of a wide range of toxic pollution components,
and it has an extremely high “intake fraction,” meaning human exposure is
disproportionately greater than average atmospheric concentrations.
Moreover, wood smoke itself is uniquely toxic, probably more so than any
other common type of urban pollution. As a result, it deserves special
attention from lawmakers and regulators beyond what would be warranted
within the context of a PM2.5 State Implementation Plan (SIP) control
strategy or its contributions to the exceedance of National Ambient Air
Quality Standards (NAAQS). Any public policy incentivizing the trading in of
old wood stoves for newer “EPA-certified” stoves as a substitute for burning
bans is misguided and inadequate, because homeowners will still be left
with heating devices that are far more polluting than other alternatives.
Utah Physicians for a Healthy Environment (UPHE) is the largest civic
organization of health care professionals in Utah, with about 340 members
whose areas of expertise include virtually every medical specialty and
related disciplines such as biology, genetics, chemistry, toxicology,
ecology, atmospheric modeling, and engineering. The health effects of air
pollution represent the core of our expertise and therefore our engagement
in public policy. UPHE has made note of the withdrawal of the woodburning
ban proposal by Governor Gary Herbert and the Utah Division of
Air Quality. Nonetheless, UPHE wishes to register this report with the Utah
Air Quality Board (AQB) in support of the proposal, and in fact raise issues
associated with the burning of solid fuel that were not addressed by the
A strong case can be made that air pollution is the largest public health
threat in most urban areas and with more consequence than smoking.
Every breath that every person takes—including pregnant women, infants,
and children—is contaminated by air pollution to some degree. In contrast,
smoking is limited to a fraction of the population, and even smokers only
inhale cigarette smoke during a small percentage of their total daily
respirations. Worldwide deaths due to cigarette smoking are estimated at 5
million per year,85 and the World Health Organization (WHO) estimates air
pollution kills 8 million people per year.86 Furthermore, smoking is
“voluntary” air pollution exposure, while community air pollution is primarily
involuntary; this is particularly true in the case of wood smoke.
Air pollution in general is increasingly recognized as a systemic health
threat, impairing the functioning of virtually every organ system, and related
to the same broad spectrum of disease outcomes as cigarette smoke.
Because of this, UPHE proposes for consideration by the AQB a rule that
would address wood burning by residents, restaurants, unregulated
incinerators used by small businesses, and the growing popularity of
essentially unregulated household incinerators, only under a new name
that suggests a desirable property amenity—“backyard fire pits.”
Burning trash in backyard incinerators has long been prohibited in most
urban areas, and the justification is obvious. Operating a vehicle with
excessive emissions has long been prohibited through emissions
inspections. The rationale has been accepted that even though it may be
cheaper for the owner of an older, more polluting vehicle to continue to
operate that vehicle, for the public good those vehicles must be cleaned up
or retired. Why should home heating devices be any different?
Furthermore, comparing wood-burning devices used during the winter
season to auto emissions, by various metrics it is a fair approximation that
one household burning wood all winter produces as much pollution as
between 90 to 400 automobiles driven all winter.1 So while we have long
had in place a regulatory mechanism to limit how much pollution one
vehicle may emit, we have had no mechanism to limit how much pollution
one home may emit, despite the potential for it being a much larger source
Many years ago our society adopted a the norm that no one should be
involuntarily subjected to secondhand cigarette smoke because of the
inherent public health consequences and the infringement on the rights of
nonsmokers to avoid exposure. Routine wood-burning in an urban setting
should not be allowed for exactly the same philosophical, aesthetic and
public health reasons as prohibition of cigarette smoking in public venues,
backyard trash incineration, and excessive vehicle emissions. The smoke
from wood stoves, fire pits, boilers and fireplaces creeps onto adjacent
property and into nearby homes, affecting the quality of life and health of
neighbors. Cheap heat or pleasant ambiance for a resident burning wood is
engaged in at the expense of nearby neighbors and the community at
large, just like secondhand cigarette smoke.
1. Wood smoke is a surprisingly large contributor to
overall community pollution levels.
Wood burning has an enormous impact on community-wide pollution
levels. Source apportionment studies have estimated that wood/biomass
combustion contributes 10 percent to 60 percent of the fine-particle
concentrations (PM2.5) in large cities, such as Seattle, Phoenix, Beijing,
Prague and Helsinki.2,3,4,5 In Pierce County, Washington, 53 percent of
PM2.5 emissions comes from wood. A study in Los Angeles showed that in
the winter, residential wood combustion there contributed 30 percent of
primary organic aerosols (probably the most important mass component of
particulate pollution), more than motor vehicle exhaust, which contributed
21 percent.6,7 In Fresno, California, wood smoke contributed on average 41
percent of organic carbon and approximately 18 percent of total PM2.5
mass.8 A study in two San Jose, California, locations showed that wood
smoke pollution was 4.4 times that of gasoline- or diesel-fueled vehicles.104
There is no reason to think that Utah’s largest cities would be much
different. In fact, the common figure recited by the media, and even the
governor—that wood smoke is “5 percent” of the problem—is a complete
misunderstanding and/or mischaracterization of the “the problem.” The
source of the “5 percent” number is a study published by AQB member
Kerry Kelly.9 About one-third of the total PM2.5 emissions is “primary;” the
rest is “secondary” (formed in the atmosphere from precursor gases).
About one-third of the primary PM2.5 emissions was from wood burning
and cooking combined—specifically, 38 percent, compared to 35 percent
for all cars and trucks when the PM2.5 emissions was above 20 μg/m3. If
residential wood burning is half of the wood/cooking inventory, 5 percent is
the result of 1/3 x 1/3 x 1/2. So while 5 percent seems like a small number,
the study shows residential wood burning and grilling are as much of the
“problem” as all of our vehicles. But the bulk of medical research indicates
that “primary” PM2.5 emissions are much more toxic than “secondary”
PM2.5 emissions, making the real threat much greater than “5 percent”
suggests. This study further speaks to the inadequacy of the current woodburn curtailment program in controlling the problem.
A recent program initiated in the San Joaquin Valley Air Basin (SJVAB) to
reduce wood smoke demonstrated an improvement in air quality related to
even a modest program to reduce wood burning. Within three years, a
reduction of 15 percent in PM2.5 levels and 13 percent in hospitalizations
for ischemic heart disease was achieved in their urban areas.97 Bear in
mind, this program did not incorporate a season-long ban, and the average
wintertime temperatures in the SJVAB are ten degrees warmer than in Salt
Lake City. Therefore, any program to reduce or ban wood smoke in Utah’s
urban areas would undoubtedly achieve even greater reductions.
According to the California Environmental Protection Agency Air Resources
Board, the inhalable particle pollution from one wood stove is equivalent to
the amount emitted from 3,000 gas furnaces producing the same amount of
heat per unit. While so-called EPA-certified wood stoves might burn
cleaner, they cannot begin to approach the much lower emissions levels of
natural gas furnaces.
2. Wood smoke is not evenly distributed throughout the airshed.
Severe hot spots of pollution and “local victims” are created.
A study in Seattle during winter months showed much higher increases in
particulate pollution in residential areas where wood burning occurred,
compared to the business district—67 percent compared to 9 percent.10
Another study revealed that about 90 percent of fine particulate pollution in
a Tacoma neighborhood came from wood burning.11, An EPA study states
that “In some neighborhoods, on some days, 90% of the particle pollution is
from residential wood burning.” 103
Unlike most other sources of pollution, wood-burning emissions in a home
are released directly into the area where people spend most of their time,
at an elevation that does not promote dispersion. A recent study in Finland
confirmed both the greater impact of wood burning compared to vehicle
emissions and the concentration effect near its sources.108 Studies from
California show that within a single square kilometer of a residential area,
concentrations of wood smoke can vary as much as 2,500 times.12 The
highest measured concentrations were up to 100 times higher than the
community average. A single wood-burning household can envelope
adjacent and downwind homes with a primary PM0.1 (the most dangerous
subset of PM2.5) plume. This demonstrates how significant the creation of
“local victims” is in assessing the true extent of the health impacts of wood
burning. Smoking on airplanes or in public buildings is not prohibited
because of what that does to community PM2.5 levels. It is prohibited
because of the direct public health consequences to those in the immediate
area. The same consideration and protection should apply for neighbors in
the issue of wood burning to prevent “local victims.”
“The largest single source of outdoor fine particles (PM2.5) entering into
our homes in many American cities is our neighbor’s fireplace or wood
stove. … Only a few hours of wood burning in a single home at night can
raise fine-particle concentrations in dozens of surrounding homes
throughout the neighborhood and cause concentrations of PAHs (polycyclic
aromatic hydrocarbons)—one of the most toxic compounds of air pollution
—higher than 2,000 ng/m3.” (Dr. Wayne Ott, Stanford University, Feb. 1,
1998). Background concentrations of PAHs should be close to zero.
Wood smoke is not just an outdoor problem. In houses without current
wood burning, fine-particle levels are usually lower than outdoor levels. But
in areas with high levels of wood smoke, even houses not using wood
stoves or fireplaces have higher indoor wood smoke levels. Wood smoke
particles are very small (ultrafine), ranging from 0.2 microns at the start of
the burn period to .05 microns as the burn cycle progresses. Particles of
this size behave like gases. There is no practical way to prevent wood
smoke pollution from seeping into nearby homes. The extremely small size
of the particles results in the particles remaining suspended in the
atmosphere for long periods of time, making a disproportionate contribution
to airshed pollution. Stagnant conditions and winter temperature inversions
result in wood smoke hanging close to the ground, easily penetrating
homes and buildings.
A study by the University of Washington showed that 50 percent to 70
percent of the outdoor levels of wood smoke were found in nearby homes
that were not burning wood. The EPA did a similar study in Boise, Idaho,
with similar results.13 A study in California showed an even higher result:
Indoor wood smoke was found to average 88 percent, as high as outdoors.
1 If a homeowner follows current Salt Lake County rules recently
established by the Salt Lake County Board of Health, and doesn’t burn
during “yellow” or “red” alerts days, but does burn during all “green” days,
his/her neighbors can go an entire winter without having even one day of
An important concept in pollution and public health is that of population
“intake fraction.” Intact fraction is the mass of pollutant inhaled divided by
the mass emitted. Obviously, regarding health consequences, what is
inhaled is what matters, much more so than what is emitted. Two different
pollution sources with comparable emission rates of the same pollutant can
have significantly different intake fractions, depending on the surrounding
population density and the juxtaposition of the point of release. Wood
smoke has a uniquely high intake fraction. During the winter, people spend
about 90 percent of their time indoors, and most of that time is spent in
their own homes. Residential wood smoke is the only major pollution
source that is released exactly in the area where people spend most of
their time, at a height where dispersion is minimal. Some pregnant women
and some children spend even more of their time at home. For many
physiologic, metabolic and developmental reasons, children and fetuses
are well known to be much more sensitive to pollution’s health impacts,
with the potential for long-term health impacts. The public health
consequences of in-home and neighborhood wood smoke are magnified
further because many members of the most vulnerable subset of the
population are the most exposed.
The concept of “intake fraction” raises a troubling irony—people who burn
wood are their own worst victims, subjecting themselves and especially
their children (more than anyone else) to increased pollution levels.
Particulate levels were found to be from 26 percent14 to as much as 500
percent higher in the indoor air of wood-burning homes compared to non–
wood-burning homes,15 and levels far beyond “red alert” conditions.
Benzene levels were 29 percent higher.16 Average levels of the highly toxic
PAHs were 300 percent to 500 percent higher.17
Children living in homes where wood is regularly burned were much more
likely to have severe respiratory symptoms compared to non–wood-burning
controls.18 Children in Klamath Falls, Oregon, showed decreases in lung
function during the wood-burning season in those parts of the city with the
highest amount of wood-burning.19 Numerous studies of adults show the
same general trend of increased symptoms of respiratory disease among
those living in residences with fireplaces or wood stoves in use.
Wood boilers deserve special mention and condemnation as severe health
hazards because of their shockingly high pollution results. In a 2006 report
from Northeastern States for Coordinated Air Use Management
(NESCAUM), wood boilers were found to produce PM2.5 levels over 1,000
μg/m3 periodically, with frequent values over 400 μg/m3 during routine
operation of the boiler, with levels measured up to 150 feet away. Peak
levels measured at 50, 100, and 150 feet from the stack often reached over
4,000 μg/m3, including an astounding 8,800 μg/m3 peak measurement at
50 feet away.
3. Wood smoke is even more toxic than other particulate pollution.
The Canadian government’s official website, Healthy Canadians, states
boldly and unequivocally, “Avoid Wood Smoke.”96 Wood smoke is an
extreme public health hazard, containing over 200 toxic chemicals and
compound groups. The emissions from wood smoke are almost entirely in
the inhalable size range.20 A study in Vancouver reported that wood smoke
particles are seven times more likely to be breathed into our lungs than the
average PM2.5 particle in Vancouver’s air.21,22 Once inhaled, the small
particles that are characteristic of wood smoke also more easily penetrate
cell walls and even subcellular structures, such as mitochondria and the
cell nucleus.87 It is at this microscopic, cellular level that particulate matter
triggers its broad array of health consequences.
Components of wood smoke are similar to those of cigarette smoke. Both
types of smoke include particulate matter, carbon monoxide, formaldehyde,
sulfur dioxide, nitrogen oxides, dioxins, and polycyclic aromatic
hydrocarbons (PAHs).23 Furthermore, as with cigarettes, those who are
doing the wood burning are the most victimized by the pollution generated.
A report by Environment & Human Health, Inc., “The Health Effects of
Wood Smoke,” cites medical research indicating that wood smoke
interferes with lung development in children and increases a child’s risk for
serious lower respiratory infections, such as bronchitis and pneumonia.24
Wood smoke exposure can depress the immune system, damage the
pulmonary epithelium25 and increase arterial stiffness.26
The very small size of the particulate emissions and high levels of PAHs
from wood smoke may account for its excessive toxicity compared to fossil
fuel-generated particulate matter. Ultrafine particles are more potent in
inducing inflammatory responses in the human body than fine particles.
27,28,29,30,31,32 Wood smoke produces high levels of free radicals, leading to
DNA damage as well as inflammatory and oxidative stress responses in
gene expression in cultured human cells.33,34 Exposure to PAHs has been
associated with mutations in tumor suppressor genes.
The federal Environmental Protection Agency estimates that the lifetime
cancer risk from wood stove smoke is twelve times greater than that from
an equal volume of secondhand tobacco smoke. (The Health Effects of
Wood Smoke, Washington state Department of Ecology). Organic extracts
of ambient particulate matter containing substantial quantities of wood
smoke are 30-fold more potent than extracts of cigarette smoke
condensate in a mouse skin tumor-induction assay that was conducted.35
Wood smoke exposure approximately doubles an individual’s risk of getting
lung cancer92,93 and cancers of the mouth and throat.94 One study showed
a significant increase in childhood brain tumors with prenatal and postnatal
exposure to wood smoke.90 PAH attachment to DNA (DNA adducts) has
been specifically correlated with higher rates of breast cancer.
Studies of cigarette smoke and automobile traffic-generated pollution show
that significant epigenetic changes, e.g., genotoxicity, can occur literally
within minutes or hours after exposure,83,84 so there is every reason to
believe that wood smoke would act just as quickly. Smokers exposed to
wood smoke, either through home heating andcooking or through
neighborhood pollution, are not only at increased risk of chronic obstructive
pulmonary disease (COPD), but they are also more likely to have
epigenetic changes in their DNA that synergistically increases their risk of
COPD and related pulmonary problems, and likely also lung cancer.91
Wood smoke particles have been reported to induce DNA damage in vitro
in human monocytic and epithelial cell lines and in a murine macrophage
cell line. However, particles from poor combustion—e.g., low-temperature
wood boilers and other inefficient wood-burning appliances—seem to have
greater effects on both cytotoxicity and DNA damage than particles from
more complete combustion conditions.88,89
Free radicals produced from wood smoke are chemically active for twenty
minutes. In contrast, tobacco smoke free radicals are chemically active for
thirty seconds. Wood smoke free radicals may attack our body’s cells up to
forty times longer once inhaled.36 Animal toxicology studies show that
wood smoke exposure can disrupt cellular membranes, depress
macrophage activity, destroy ciliated and secretory respiratory epithelial
cells, and cause aberrations in biochemical enzyme levels.37
POLYCYCLIC AROMATIC HYDROCARBONS (PAHs)
Undoubtedly, making a major contribution to the toxicity of wood smoke is
the high concentrations of PAHs. The EPA estimates that a single fireplace
operating for one hour, burning ten pounds of wood, will generate more
PAHs than 6,000 packs of cigarettes.38 Other estimates indicate an even
higher rate of PAH release.39,40 Wood burning is the largest source of
PAHs in the urban environment. In urban circumstances where wood
burning is common in the winter, atmospheric PAH concentrations can be
15 times higher during the winter than during the summer.100,101
Furthermore, wood-burning appliances with similar emission profiles for
particulate matter may simultaneously produce dramatically different
amounts of PAHs.41
Adverse health effects far beyond carcinogenicity add to the need for
community control strategies to reduce wood smoke, which should be a top
priority in any overall pollution reduction strategies.
PAHs have been implicated in numerous studies showing adverse
pregnancy outcomes and impaired fetal development, including birth
defects. Prenatal exposure to PAHs has been found to adversely change
placental vascular architecture, trigger pro-carcinogenic epigenetic
changes, and is associated with decreased intelligence, higher rates of
behavioral and attention deficit disorders, and obesity.42,43,44,45,46,47,48,49,50
DNA damage induced by PAH exposure has been demonstrated by
numerous studies. Fetuses are far more susceptible to DNA damage and
pro-carcinogenic epigenetic changes than are adults.95
A remarkable new study showed a direct linear relationship between the
amount of PAH exposure during pregnancy and MRI scans that
documented loss of volume in brain white matter and loss of intelligence
and behavioral disorders in children 110
Furthermore, PAH from wood smoke will land on indoor household and
outdoor surfaces and soils, resulting in second- and third-hand ingestion
and skin absorption. Studies done in soil near oil refineries (whose
emissions are also high in PAHs) have shown concentrations as high as
A complete review of the toxicity of the group of chemically related
compounds called dioxins is beyond the scope of this review. Nonetheless,
dioxins deserve special mention. Wood smoke is the third largest source of
dioxin exposure in the United States.52 Dioxin levels are typically measured
in picograms, one trillionth of a gram. Burning just one kilogram of wood
produces as much as 160 micrograms of dioxins.53
An Australian study found that wood heaters were responsible for
increasing background dioxin concentrations by ten times compared to
during the non-heating season.54 The burning of wood pellets and other
forms of treated wood has the potential to release even higher
concentrations of dioxins. Copper, a common biocide element that is
chemically bound to wood, is an important dioxin catalyst. Preservative
metals promote smoldering of wood char following the cessation of flaming,
providing the required temperature environment for dioxin formation, and
chlorinated organics added as secondary preservative components yield
dioxin precursors upon thermal decomposition.55
Dioxins are among the most toxic compounds to which humans can be
exposed. Dioxins, and many of the other chemicals in wood smoke, are
exactly the type of chemicals that the American College of Obstetricians
and Gynecologists and the American Society for Reproductive Medicine
addressed in a prepared statement in autumn 2014.
“Reducing exposure to toxic environmental agents is a critical area of
intervention for obstetricians, gynecologists, and other reproductive
health care professionals. Patient exposure to toxic environmental
chemicals and other stressors is ubiquitous, and preconception and
prenatal exposure to toxic environmental agents can have a profound
and lasting effect on reproductive health across the life course.
Prenatal exposure to certain chemicals has been documented to
increase the risk of cancer in childhood…[we] join leading scientists
and other clinical practitioners in calling for timely action to identify and
reduce exposure to toxic environmental agents while addressing the
consequences of such exposure.”56
Dioxins fall into the broad category of endocrine disruptor chemicals. The
Endocrine Society, internal medicine specialists in diseases of the
pancreas, thyroid, adrenal and pituitary glands, and hormone dysfunction,
issued this statement about dioxins in 2010:
“Even infinitesimally low levels of exposure indeed, any level of
exposure at all, may cause endocrine or reproductive abnormalities,
particularly if exposure occurs during a critical developmental window.
Surprisingly, low doses may even exert more potent effects than higher
Dioxins, like PAHs, are a particularly significant threat to fetuses and
infants. Greater levels of dioxin exposure are associated with pregnancy
loss and pre-term delivery,58 impaired fetal growth and smaller birth size,
including smaller head size.59 Dioxins also cause immunosuppression.
Prenatal exposure is associated with a 250 percent to 500 percent increase
in episodes of otitis media in 18-month-olds.60 Many chemicals, such as
dioxins, have been shown to not only impair the health of those exposed
but through epigenetic changes to also impair the health of subsequent
generations who are not exposed.61
Acrolein is a chemical found in high concentrations in both cigarette and
wood smoke. Acrolein is well known to suppress the immune system62 and
has recently been strongly implicated in demyelinating diseases, such as
multiple sclerosis.63,64 The authors of a recent study stated, “We think that
acrolein is what degrades myelin. … We’ve discovered that acrolein may
play a very important role in free radical injury, particularly in multiple
sclerosis.” One day’s worth of wood burning for an average household
produces as much acrolein as 26,000 cigarettes.
Several studies suggest that particulate pollution in wood smoke from
wildfires is much more toxic to lung macrophages than an equivalent
concentration of similarly sized particulate pollution found in typical urban
smog.65,66,67,68 A recent study demonstrated lower birth weights among
babies born to mothers who were pregnant during a two-week stretch of
severe wildfires in Southern California.69
A study of a population in Peru demonstrated significantly higher blood
pressures among those living in homes that burned wood, compared to
those that didn’t. Wood and other biomass fuel users had systolic blood
pressures that averaged seven mmHg higher, and diastolic blood
pressures that averaged almost six mmHg higher compared to nonburners.
That is a remarkable difference, and, considering all the
consequences of a higher blood pressure, one to have serious
consequences for all cardiovascular related health complications.109
Another recent study compared daily hospital admissions and death rates
related to cardiovascular and pulmonary diseases in two cities in South
America where one city’s pollution was predominantly from wood smoke
and pollution in the other was from mobile and typical point sources.
Compared to the non–wood-burning city, the city with primarily wood
smoke experienced an increase of 47 percent for cardiorespiratory deaths
and an increase of 104 percent for respiratory hospital admissions for every
10 μg/m3 increase in PM10.70
4. “EPA-certified stoves” are not the solution.
“No natural gas service” is no longer an excuse.
Not surprisingly, the Hearth, Patio and Barbecue Association (HPBA) has
been mounting a campaign to not only fight any banning of wood burning
but also to convince policy makers that the answer to wood smoke is to sell
more of their product, not less. Below are eight reasons that policy makers
should not accept this rationale.
1. EPA stove performance in the real world does not match their
performance as tested in the lab, something that the manufactures and
the EPA acknowledge.71,72 For example, current testing standards
specify the use of kiln dried lumber precisely arranged in a crib formation
—hardly representative of the way most stoves are actually operated.
Emission rates reported in the certification process do not represent
emission levels of stoves in homes after extended use.
The wood-burning-device industry (HPBA) and the EPA claim that wood
stoves emit 70 percent less particulate matter, and therefore the answer
to community problems with wood burning is to sell more of these
products, not ban them. However, the EPA’s program in Libby, Montana,
is proof in the real world that those claims are exaggerated. The woodburning
industry, the EPA and the state paid to change out every wood
stove in the Libby area to an EPA-certified stove. They also invested in
education programs and proper installation. Yet using industry’s own
numbers from an industry-funded study, particulate matter (PM) was
reduced by only 28 percent. If EPA stoves performed as claimed, PM
reduction should have been 56 percent. Before the change-out, 83
percent of Libby’s winter PM came from residential wood burning. If the
subsidies had gone to change to propane or electric heat, PM levels
would have dropped almost 80 percent, while also reducing toxics and
Another change-out study in Idaho found that almost 33 percent of the
homes where EPA-certified stoves replaced older models showed
increases in indoor particulate matter.73 A study prepared for the EPA
showed that after extended use, actual emissions were over three times
greater than the certified values.74
The consistency and reproducibility of wood-heater emissions testing is
very poor. Many relatively small, uncontrollable variables that are
inherent in the wood combustion process, such as type of wood,
substrate configuration and moisture content, can combine to
significantly affect the outcome of any given test.75 The emissions from
modern combustion appliances for wood logs may increase 10-fold if
they are not operated appropriately.76
2. Wood stoves generate a large amount of emissions when they are
started up, but these emissions are not “counted” in the EPA testing
procedure. Testing does not begin until the stove has begun to burn
3. EPA wood stoves have never been shown to reduce the amount of the
most deadly components of wood smoke, including dioxins, furans, and
PAHs. Some studies have shown that EPA stoves emit even more of
these highly toxic compounds.77,78,79
4. In-home performance is too dependent on the operator—airflow and fuel
choice radically affect the actual emissions. A stove poorly operated or
maintained can emit ten times more pollution than lab testing indicates.
John Gulland, manager of the “pro-wood” Wood Heat Organization, puts
it this way: “People who don’t care about the impacts of their actions on
neighbors and are content to remain ignorant of good wood-burning
practice will make a lot of smoke, regardless of the emissions rating of
the appliance they choose.”80
5. Typical wood-stove operation employs “dampering down” at bedtime or
during temperate weather. Since oxygen is a necessary component of
combustion, this can create much higher levels of pollutants.
6. The performance of wood-heating devices equipped with catalytic
components degrades over time—if poorly maintained, in as little as two
years.98 Structurally, wood heaters also degrade with use, and emission
factors increase. The negative consequences of degraded catalytic
components, which can include dramatically increased emissions, occur
outside the end-user’s home. Thus, there is no reason to think that
owners will replace the degraded catalytic components or expend the
effort and money to maintain them properly.81
7. Even if wood stoves and their pollution control devices did not degrade
over time and if they were all operated the way they are tested in the lab,
they are still hundreds of times dirtier than a natural gas furnace in
emitting particulate pollution and even more so in emitting hazardous air
pollutants (dioxins, furans, PAHs and heavy metals).
8. Exempting supposedly “cleaner” stoves from any wood-burning ban
would only make sense if combined with emissions verification by actual
testing in the field on a regular basis, just like how cars are tested. That
would be difficult, impractical and costly but is likely to produce greater
pollution reductions than the current vehicle emissions program.
Emissions checks could be paid for by a licensing fee like the one
required for automobiles.
Lack of natural gas service is no longer an excuse to have to burn wood.
From a report from Families for Clean Air99:
“The reliance on wood burning for home heating in these areas is
rationalized on the basis that the cost of electric heat or propane is
too expensive. This rationale has even held sway with air quality
regulators, who have exempted areas not serviced with natural gas
from wood burning restrictions on days when the air quality is poor or
predicted to be poor.
“But now, thanks to advances in technology, heating a home with an
electric split ductless heat pump is cheaper than heating with natural
gas. Split ductless heat pumps are extremely efficient because they
move heat from one place to another rather than generating heat
from energy. Installation does not require ductwork, which can be
expensive and difficult to put in. In fact, the cost to purchase and
install a split ductless unit is comparable to the purchase and
installation of a wood stove. Note that these split ductless heat pump
units can cool as well as heat.
5. Inversion season is not the only time we are at
risk from wood smoke.
There is no safe level of air pollution. Medical research has well established
that one unit of air pollution emitted into the community airshed when levels
are relatively low has as much, or even greater, health impact as when PM
or ozone concentrations are higher. In fact, plotting a curve correlating
sudden cardiac death (the signature outcome of PM exposure) vs.
concentration of PM yields a curve whose steepest part is at the lowest
doses.82 In other words, eliminating wood burning in circumstances that
already meet the NAAQS may be even more important in protecting public
health. This is not factored into NAAQS, but it is nonetheless an important
consideration in regulating the creation of wood smoke.
The Bay Area Air Quality Management District estimates that more than $1
billion worth of medical expenses are caused by burning wood smoke in
the Bay Area, including the calculation that one wood fire can cost your
next-door neighbor an average of $40 in medical expenses.
6. Wood smoke is a large community economic liability,
and it contributes significantly to global warming.
The Bay Area Air Quality Management District estimates that more than $1
billion worth of medical expenses are caused by burning wood smoke in
the Bay Area, including the calculation that a single wood fire can cost your
next-door neighbor an average of $40 in medical expenses.
Given the overwhelming scientific consensus regarding a growing, primarily
human-caused climate crisis, it is also important to consider the carbon
footprint of wood burning. The 2007 Nobel Prize-winning Intergovernmental
Panel on Climate Change (IPCC), consisting of approximately 2,000
scientists, concluded that black carbon soot, which is a major component of
wood combustion, is a significant “forcer” of global warming. However, a
2013, 232-page report from 31 international scientists using data collection
over four years105 concluded that the real global-warming impact of black
carbon soot was double that of previous estimates. In fact, black carbon
particulates may have a warming effect two-thirds as great as CO2.
Black carbon exerts multiple effects, depending on complex altitude and
atmospheric conditions. Black soot particles on snowpack decrease the
reflection of sunlight and cause atmospheric warming and accelerated melt
of snowpack, which is essentially a loss of available water. Dust from the
Southwest has already been shown to hasten the melting of snow in the
Rocky Mountains, reducing the amount of runoff into the upper Colorado
River by 5 percent, ultimately causing a loss of 250 billion gallons of water
a year.106,107 All particulate matter emitted along the Wasatch Front,
including that from wood burning, will have the same type of effect on
Wasatch Front snowpack, aggravating our water supply woes.
Black carbon particles heat up the layer of the atmosphere where clouds
are forming, promoting cloud evaporation, no longer allowing sunlight to be
reflected back into space. Black carbon also has cooling effects, but
considering both the warming and cooling effects, the amount of extra
energy stored in the atmosphere due to black carbon is 1.1 watts per
square meter of the earth’s surface.105 The same calculation for CO2 is
1.56—particulate pollution has two-thirds the impact of CO2.
A 2010 study concluded that the amount of carbon released per unit of
energy produced is actually greater for wood than it is for fossil fuels. It is a
common misconception that burning wood is carbon neutral. Considering
the entire carbon life cycle of wood, burning releases carbon now when we
can least afford to do so—carbon that would otherwise have been stored
for decades or perhaps centuries. While sustainable forestry practices can
help repay that “carbon debt,” those benefits do not accrue until the distant
future, too late to be of much help. As a result of this study, the state of
Massachusetts changed its renewable portfolio standard to exclude
biomass projects with long carbon payback periods.
The UN Environment Program and the World Meteorological Organization
recommended phasing out log-burn ing stoves in developed countries to
reduce global warming as well as dangerous air pollution. 111 Even if the
wood is from a sustainable source, methane and black carbon emissions
from log-burning stoves cause more global warming than a gas heater or
electric heat pump. 112
We believe that government agencies have the authority—indeed the
obligation—to make rules regarding wood-burning devices stricter than
current rules. The fact that these wood-burning devices already exist, that
companies make a profit manufacturing them, and that many people
choose to use them for reasons such as cost, convenience, or ambiance, is
no excuse for government agencies not to fulfill their obligation to protect
public health. Frankly, federal, state and local governments cannot protect
wood-burning manufacturers and wood burners and simultaneously protect
public health, and it is clearly mandated to do the latter.
It is long overdue for us to consider that subjecting one’s neighbors to the
high pollution consequences of wood-burning devices is as much of an
anachronism as allowing cigarette smoking on airplanes. The medical
science demands that the EPA act aggressively to curtail, as much as is
legally possible, this serious public health menace.
Brian Moench, MD
President, Utah Physicians for a Healthy Environment (UPHE)
Executive Director, UPHE
Cris Cowley, MD
Vice President, UPHE
Howie Garber, MD
Board Member, UPHE
Rich Kanner, MD
Board Member, UPHE
Ellie Brownstein, MD
Board Member, UPHE
Todd Seymour, MD
Board Member, UPHE
Michael Woodruff, MD
Board Member, UPHE
Board Member, UPHE
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